The objective of this research is to produce an experimentally induced phenylketonuric state in the maternal rat, approximating the human maternal phenylketonuric condition, and to investigate several parameters associated with the hyperphenylalaninemia. In order to accomplish these objectives, it is the intention of the investigator: 1) To induce a sustained hyperphenylalaninemia in maternal rats using para-chlorophenylalanine (pCl-Phe) and exogenous phenylalanine, then to describe the effects of the maternal hyperphenylalaninemia on maternal, fetal, and neonatal growth patterns and some tissue amino acid levels; 2) To study the nuclear acidic protein profiles of neonatal rat brains exposed in utero to hyperphenylalaninemia induced in the maternal animal, using an improved bisacrylamide gel electrophoresis system; 3) To investigate the anorexia and maternal muricide associated with pCl-Phe administration, describing the effects which various drugs and experimental conditions have on these phenomena; 4) To determine a relationship between experimentally induced phenylketonuria, brain free polyribosomal disaggregation, and indole metabolism in the brain; 5) To conduct, in collaboration with investigators in associated disciplines, behavioral studies using neonatal rats exposed to maternal hyperphenylalaninemia in utero, and neonates treated individually to induce hyperphenylalaninemia; 6) To complete a histological examination of the postnatal myelin development of the offspring of hyperphenylalaninemic maternal animals.